1. Field of the Invention
The present invention relates to an information recording medium, a recording apparatus, a reproduction apparatus, a recording method, a reproduction method, and a defect management method providing improved reliability on information.
2. Description of the Related Art
As large capacity information recording media, optical discs such as, for example, DVDs (Digital Versatile Discs) are known. Along with the increase in the amount of information to be recorded on an information recording medium, high density recording technology and large capacity technology have remarkably improved. As such technologies are improved, it is becoming more and more important to guarantee reliability of recorded information.
FIG. 9 shows a logical structure of a conventional information recording medium 900.
The information recording medium 900 includes a data recording area 901, a first disc information area 902, and a second disc information area 903.
The data recording area 901 includes a user data area 904 in which user data is to be recorded, and a spare area 905. When the user data area 904 has a defect area, the user data which is to be recorded in the defect area is recorded in the spare area 905 instead of a portion of the user data area 904 corresponding to the defect area.
The first disc information area 902 includes a first defect management information area 906 and a second management information area 907, both having defect management information for managing the defect area (for example, a defect block) existing in the user data area 904 and the spare area 905 having the user data recorded therein instead of the defect area.
The second disc information area 903 includes a third defect management information area 908 and a fourth defect management information area 909, both having defect management information for managing the defect area existing in the user data area 904 and the spare area 905 having the user data recorded therein instead of the defect area, as the first disc management information area 902.
The defect area existing in the user data area 904 can be managed by slipping algorithm or linear replacement algorithm (see, for example, ECMA-272 “120 mm DVD Rewritable Disk (DVD-RAM)”). In the case of slipping algorithm, the user data which is to be recorded in the defect area skips the defect area and slips to a subsequent portion of the user data area 904. Thus, the user data is recorded in a portion in the user data area 904 which is not the defect area. In the case of linear replacement algorithm, as shown in FIG. 9, the user data which is to be recorded in the defect area is recorded in the spare area 905 instead of the defect area. In both of the slipping algorithm and linear replacement algorithm, the defect management information for managing the defect area is recorded in each of the first defect management information area 906, the second defect management information area 907, the third defect management information area 908, and the fourth defect management information area 909.
As described above, the defect management information is multiplex-recorded on an information recording medium since the defect management information is important information. The reasons for this are: (i) the defect management information itself cannot be a target of defect management; and therefore, if the defect management information area, in which the defect management information is to be recorded, has a defect area, the defect management information recorded on the information recording medium cannot be reproduced; and (ii) if the defect management information is lost, the user data recorded on the information recording medium cannot be reproduced. A medium having the defect management information multiplex-recorded thereon enjoys improved reliability, since even if at least one of a plurality of units of defect management information is not reproduceable, the defect management information which has been normally reproduced is used so that the user data can be reproduced without being lost.
FIG. 10 is a schematic view of a conventional information recording medium 1001. The information recording medium 1001 includes a first defect management information area 1002 and a second defect management information area 1003, in each of which defect management information is to be recorded. The first defect management information area 1002 and the second defect management information area 1003 are located proximate to each another. The information recording medium 1001 has a defect area 1004. The defect area 1004 is, for example, a fingerprint, dust, or a scratch. User data cannot be recorded in the defect area 1004. User data recorded in the defect area 1004 cannot be reproduced.
As shown in FIG. 10, the defect area 1004 exists over the first defect management information area 1002 and the second defect management information area 1003. The information recording medium 1001 can include two units of defect management information (i.e., defect management information recorded in the first defect management information area 1002 and defect management information recorded in the second defect management information area 1003), but neither unit of defect management information can be recorded or reproduced due to one defect area 1004. In such a case, the user data recorded in the user area cannot be reproduced and thus the reliability of the user data is lowered.
FIG. 11 is a schematic view of another conventional information recording medium 1101. The information recording medium 1101 includes a first defect management information area 1102 and a second defect management information area 1103, in each of which defect management information is to be recorded. The first defect management information area 1102 and the second defect management information area 1103 are located so as to substantially face each other. The information recording medium 1101 includes a defect area 1104. The defect area 1104 is, for example, a fingerprint, dust, or a scratch.
As shown in FIG. 11, the defect area 1104 exists in the first defect management information area 1102. Namely, information cannot be recorded to or reproduced from the first defect management information area 1102. However, the information can normally be recorded to or reproduced from the second defect management information area 1103. In such a case, the user data recorded in the user data area can be reproduced using the defect management information in the second defect management information area 1103, and therefore the reliability of the user data is not damaged.
As described above with reference to FIGS. 10 and 11, the possibility of defect management information being normally reproduced is raised by locating defect management information areas, in which the defect management information is to be recorded, at discrete positions in the information recording medium. Specifically, it is desirable to locate the defect management information areas so as to face each other as shown in FIG. 11.
In conventional information recording media, the positional arrangement of defect management information areas are determined in accordance with the recording density of the information recording medium. Therefore, the defect management method needs to be changed in accordance with the recording density. In an information recording medium having a fixed positional arrangement of defect management information areas regardless of the recording density, it is not necessary to change the defect management method but there is a risk of the defect management information areas being close to each another.